High temperature composite structure and system for detecting degradation thereof

ABSTRACT

The present disclosure includes a system and method for monitoring degradation of a high temperature composite component (HTC). The HTC is defined by a volume that includes a matrix material and a fiber formed from at least one of ceramic and carbon material. One or more electrical conductors are disposed within the volume and connected directly or indirectly to a monitoring system.

CROSS REFERENCE TO THE PRIORITY PATENT APPLICATION

This is a Continuation Patent Application of U.S. application Ser. No.16/218,881 currently pending and filed on Dec. 13, 2018.

GOVERNMENT RIGHTS STATEMENT

The invention described herein may be manufactured and used by or forthe Government of the United States for all governmental purposeswithout the payment of any royalty.

FIELD OF THE INVENTION

This invention relates to the field of high temperature ceramic orcarbon composites. More particularly, this invention relates todetecting the structural integrity of components made from suchmaterials.

BACKGROUND OF THE INVENTION

The manufacturing process for a high temperature composite (HTC)typically consists of (1) lay-up and fixation of the fibers, shaped asthe desired component (as used herein, the term lay-up also includes apreform, as described in more detail hereafter), (2) infiltration of thematrix material, and (3) curing and firing of the HTC to drive offvolatile compounds, leaving just the HTC material remaining, namelyfiber and matrix, with the latter being ceramic or carbon-based. Thefirst and second steps can be iteratively repeated by performing apartial cure after each fixation and infiltration of a fiber ply, thenfixing, infiltrating and partially curing another ply, and so forthuntil the component is completed, and then firing the entire component.

In the first step, the fibers are arranged and fixed such as by lay-upof fabrics, winding, braiding, knotting, or by the formation of athree-dimensional preform. In the case of a preform, plies are stackedup and sequentially needled in the through-thickness direction toprovide improved inter-laminar properties. Each of these layers isreferred to as a ply herein. The end result of fixing a plurality ofthese plies is called a preform. Many different options are availablefor the second step of matrix formation, such as deposition out of a gasmixture, pyrolysis of an infiltrated pre-ceramic polymer, chemicalreaction of molten metallic precursors, and electrophoretic depositionof a ceramic powder. These are usually followed by sintering andcrystallization at temperatures of between about 1000° C. and 1700° C.

As used herein, the term high temperature composites (HTCs) refers tocomposites where both the fibers and the matrix are at least one ofceramic based and carbon based. Such HTCs are used to form componentsthat are deployed in extreme environments, such as high temperature,high stress, or high corrosion. Other types of composites, such aspolymer matrix composites (PMCs), typically cannot survive for anyreasonable length of time in these environments.

PMCs are also formed at much lower temperatures than HTCs, at less thanabout 500° C., whereas HTCs are generally fabricated at temperaturesgreater than about 1100° C. Thus, the materials and methods that areapplicable to PMCs are not applicable to HTCs.

Because HTC components are exposed to such extreme environments, theyneed to be inspected at regular intervals to detect any structuraldegradation. In the absence of such inspections, a component might fail,leading to catastrophic damages. Some of the structural problems thatcan occur are spalling, cracking, chemical reaction, and erosion(ablation).

However, removing such a component from use to perform the inspectioncan be expensive and time consuming. Further, in some applications itcan be useful to monitor any degradation of the component in real time,as it is being used.

What is needed, therefore, are structures and methods that tend toreduce the issues suggested above, at least in part.

SUMMARY OF THE INVENTION

These and other needs are met by a HTC having a volume that includes amatrix material of at least one of ceramic and carbon, fiber of at leastone of ceramic and carbon, where the fiber is dispersed within thematrix material, and electrical conductors.

In some embodiments according to this aspect of the invention, theelectrical conductors include electrically conductive surface coatingson a portion of the fibers. In some embodiments, the electricalconductors include metal wires disposed in a parallel orientation. Insome embodiments, the electrical conductors include metal wires disposedin a grid orientation. In some embodiments, the electrical conductorsinclude metal wires formed as staples buried at different depths of theHTC.

In some embodiments, portions of the electrical conductors extendoutside of the volume. In some embodiments, the electrical conductorsare wholly contained within the volume. In some embodiments, theelectrical conductors include at least one of niobium, molybdenum,tantalum, tungsten, rhenium, titanium, vanadium, chromium, zirconium,hafnium, ruthenium, rhodium, osmium iridium, and platinum. In someembodiments, the HTC is at least one of a surface, structural,propulsion, and functional component of an aircraft that is exposed toan aggressive environment. In some embodiments, the fibers are plies ofwoven fibers. In some embodiments, the fibers are plies of nonwoven websof fibers.

According to another aspect of the invention, there is described a HTChaving a volume including a matrix material comprising at least one ofceramic and carbon. The matrix material has a first conductive portionand a second nonconductive portion, where the first portion and thesecond portion are substantially non-intermixed. The volume alsoincludes fiber that includes at least one of ceramic and carbon, wherethe fiber is dispersed within the matrix material.

In some embodiments according to this aspect of the invention, the firstportion is disposed in a same position throughout a depth of the volume,while in other embodiments, the first portion is disposed in multiplepositions throughout a depth of the volume, where the first portiondisposed at one position in the depth does not contact the first portiondisposed in another position in the depth. In some embodiments, thefirst portion is comprised of the second portion plus conductiveadditives comprising at least one of refractory metallic particulate andelectrically conductive carbon-based material having at least one ofgraphene and nanotubes. In some embodiments, the HTC comprises at leastone of a surface, structural, propulsion, and functional component of anapparatus that is exposed to an aggressive environment. In someembodiments, the fiber comprises plies of woven fibers. In someembodiments, the fiber comprises plies of a nonwoven web of fibers.

According to another aspect of the invention there is described a methodfor monitoring degradation of a HTC component, where the HTC componentas provided includes a volume of a matrix material that includes atleast one of ceramic and carbon, and fiber that includes at least one ofceramic and carbon, where the fiber is dispersed within the matrixmaterial. Electrical conductors are also included within the volume.Electrical properties of subsets of the electrical conductors aremonitored, and a report is provided when the electrical properties of agiven subset of the electrical conductors crosses a predeterminedthreshold. The HTC component is selectively remediated based on thereport.

In various embodiments according to this aspect of the invention, theHTC is at least one of a surface, structural, propulsion, and functionalcomponent of an apparatus that is exposed to an aggressive environment.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages of the invention are apparent by reference to thedetailed description when considered in conjunction with the figures,which are not to scale so as to more clearly show the details, whereinlike reference numbers indicate like elements throughout the severalviews, and wherein:

FIG. 1 is a perspective view of a HTC with electrical leads according toa first embodiment of the present invention.

FIG. 2 is a perspective view of a HTC with electrical leads according toa second embodiment of the present invention.

FIGS. 3A and 3B are views of a HTC with electrical leads according to athird embodiment of the present invention.

FIG. 4 is a perspective view of a HTC with an electrically conductiveportion according to a fourth embodiment of the present invention.

FIG. 5 is a perspective view of a HTC with electrically conductiveportions according to a fifth embodiment of the present invention.

FIG. 6 is a perspective view of a HTC with embedded electricallyconductive structures according to a sixth embodiment of the presentinvention.

FIG. 7 is a perspective view of a HTC with embedded electricallyconductive structures according to a seventh embodiment of the presentinvention.

FIG. 8 is a functional block diagram of an apparatus that uses an HTCaccording to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION General Overview

According to various embodiments of the present invention, there isadded an electrically conductive system to the lay-up, such as bymodifying portions of the matrix to be electrically conductive or byadding electrically conductive structures to or between the plies. Insome embodiments the electrically conductive system spans the entire plyin which it is formed, with a plurality of conductive membersindividually formed in or between a plurality of the plies.

In some embodiments the electrically conductive system can be monitoredin-situ or ex-situ, and in other embodiments the electrically conductivesystem can only be monitored ex-situ.

Because the electrically conductive system is disposed at multiplelayers through the component, the degree of cracking, abrasion,corrosion, and ablation (all generally referred to as wear herein) tothe component can be monitored. Because the electrically conductivesystem extends, at least in some embodiments, across an entire ply inwhich it is disposed, the location and depth of such wear can bemonitored.

Specific Embodiments

With reference now to the figures, various specific embodiments of thepresent invention are described.

FIG. 1 depicts a lay-up 100 according to an embodiment of the presentinvention, with five plies 102 that have been infiltrated with a matrix106. FIG. 1 and the other figures are highly representational, in thatthey show a top-most ply 102 curled back so as to reveal the electricalconductors 104 that are disposed either within an underlying ply 102 orbetween two adjacent plies 102. The number of plies 102 in the lay-up100 is representational only, and not limiting. So too the number,shape, location, and depth of the electrical conductors 104 as depictedis representational only and not limiting.

In the embodiment of FIG. 1 , the electrical conductors 104 take theform of electrically conductive wires that come up through the bottom ofthe lay-up 100 to one or more of a plurality of different levels andpositions, in a configuration that generally resembles a staple. Byplacing these staples in positions that cover the length, width, anddepth of the lay-up—meaning from side to side, front to back, andbetween all of the plies 102, the position and depth of any wear thatthe lay-up 100 might incur can be monitored.

For example, the ends of the electrical conductors 104 can be connectedto an instrument such as a conductivity meter, and the conductivity ofeach of the individual conductors 104 can be monitored. A crack in oneposition of the lay-up 100 will tend to sever an electrical conductor104 that is disposed in that position, and the associated loss ofconductivity through the electrical conductors 104 will be detected bythe instrument, and can be reported to a controller, such as an on-boardcomputer. Thus, the computer can track the position and depth of wearwithin a given component of the apparatus (aircraft, vehicle, etc.) thatis constructed in this manner.

In a similar manner, as plies 102 are ablated away from the componentdue to heat, friction, corrosion and other factors, electricalconductors 104 will start to become open circuits at levels that aredeeper and deeper within the lay-up 100, and in this manner the computercan monitor the rate at which wear is occurring within the lay-up 100.Thus, both the position and the depth of wear can be monitored in-situor ex-situ.

FIG. 2 provides a depiction of a different structure for the electricalconductors 104, in which they form an array of crossing electrical leadsthat are disposed either within or between various layers of the plies102. In some embodiments, the wires forming the electrical conductors104 extend to the edge of the lay-up 100, and are electrically connectedto an instrument, such as a conductivity meter as described above. Insome embodiments the lateral positions of the wires of the electricalconductors 104 are offset from one layer to the next, so as to providemore finely resolved position information as electrical conductors 104are damaged and reported as open circuits.

FIGS. 3A and 3B depict various ways in which the electrical conductors104 can be formed or disposed within a ply 102. In FIG. 3A, electricalconductor 104 a is a modified fiber or fiber tow 108 (as described inregard to FIG. 3B), electrical conductor 104 b is laid on top of the ply102, and electrical conductor 104 c is woven into the ply 102.Alternately, electrical conductor 104 a can replace a fiber 108. In FIG.3B, the surface of a fiber 108 of the ply 102 has received amodification that causes a portion 110 of the fiber 108 to beelectrically conductive. This can be accomplished with the use of asurface treatment, such as a metallic coating, or by some other means.Either just a portion of or the entirety of the fiber 108 can have thesurface modification 110.

FIG. 4 depicts an embodiment where a portion 112 of the matrix 106 ismodified to be electrically conductive, such as by adding anelectrically conductive component to the material of the matrix 106. Inthe embodiment depicted in FIG. 4 , the electrically conductive portion112 of the matrix 106 is infiltrated down through all of the plies 102in the lay-up 100. In this embodiment, the degree and position of wearcan be detected by monitoring the reduction of electrical conductivitywithin a given strip of the modified portion 112. Thus, the portion 112serves as the electrical conductors 104.

In the embodiment of FIG. 5 , the electrically conductive portion 112 isonly disposed on or in some of the plies 102, such as every other ply102. In this embodiment, the degree and position of wear can be detectedby monitoring both the loss and reduction of electrical conductivitywithin the strips of the modified electrically conductive portion 112that serve as the electrical conductors 104 at different depths withinthe lay-up 100. It is appreciated that the width and number of themodified portions 112 as depicted in FIGS. 5 and 6 is representationaland not limiting. These embodiments can be monitored either in-situ orex-situ.

FIG. 6 depicts an embodiment where the electrical conductors 104, suchas wires, are disposed within or between various ones of the plies 102,but are not connected one to another, and which in some embodiments donot extend outside of the internal portions of the lay-up 100. In thisembodiment the wear that might be sustained by a given electricalconductor 104 can be detected such as with an eddy current meter, orsome other inductive device. This embodiment can also provide bothin-situ and ex-situ monitoring, but in some embodiments it is bettersuited for ex-situ monitoring.

FIG. 7 depicts another embodiment, similar to that as described inregard to FIG. 6 above, but where the electrical conductors 104 areformed with a shape that provides passive RF signaling, and thus can bemonitored using radio frequency means either in-situ or ex-situ.Currently, no embedded RF capability exists for HTCs, and therefore thisembodiment can provide a unique pattern-based signature for bothinspection and communication purposes.

The characteristics of any such antenna design would depend upon thevehicle type and mission goals, but in one embodiment would be targetedtowards long range and very long range trajectories, which are generallycovered by a frequency range of from about 300 MHz to about 30 GHz.These in turn correspond to wavelengths of from about one centimeter toabout one meter, typically using antenna elements (electrical conductors104) with dimensions that are from about two to about four timessmaller, which is very reasonable to accomplish through the proposedembodiment.

The location and shape of the electrical conductors 104 would also bevehicle and mission dependent, but since the proposed method does notconstrain or modify established manufacturing practices, it allowssignificant flexibility to integrate the antenna (electrical conductors104) at whatever locations are deemed appropriate. Connectivity of theembedded element (electrical conductors 104) to the receiver located inthe vehicle interior can be achieved by an additional through-thicknessconductor as described elsewhere herein, which can be part of theinitial antenna structure, or added subsequently during the compositelay-up, but before solidification of the matrix material of thecomposite.

From a non-operational maintenance perspective, a different kind ofembedded antenna (electrical conductors 104) can also be used for radiofrequency identification, and more specifically as a passive RFID tag toidentify individual components of the larger composite structure. Toavoid complicating the system architecture, and because these types ofreadouts can be done in ambient environments, the antenna and theintegrated circuit linked to it can be placed away from criticalstructural areas, while still being easily accessible in a maintenancedepot environment, for example. The choice of passive instead of activeRFID further simplifies the design and integration method. Oneembodiment could be intended for a frequency range of about 10 MHz toabout 15 MHz, with a readout distance of from about 1 m to about 2 m.

With reference now to FIG. 8 , there is depicted a functional blockdiagram of a system 800 that can be used to monitor and report on thecondition of an HTC component 802. The HTC component 802 is formedaccording to one or more of the embodiments described above, and is putinto service in an apparatus 804, such as an aircraft or vehicle asgenerally described herein. Although the component 802 can be used forany part of the apparatus 804, it is particularly well-suited for a partthat is exposed to an extreme environment, such as discussed elsewhereherein.

In various embodiments, the integrity of the component 802 can bemonitored by a monitor 806 either while the apparatus 804 is in use (insitu) or when the apparatus 804 is not in use (ex situ). In variousembodiments the monitor 806 takes many different forms, such as an eddycurrent meter, RFID reader, or resistometer. In some embodiments themonitor 806 is directly wired to portions of the electrical conductors104 that extend outside of the volume of the HTCs component 802, and inother embodiments the monitor 806 is able to sense the extent of anydamage to the electrical conductors 104 wirelessly, both as describedelsewhere herein.

In some embodiments the monitor 806 is under the control of or providesreadings to a controller 808, such as a computer. In some embodimentsthe controller 808 has the monitor 806 scan the entire component 802,and in other embodiments the controller 808 has the monitor 806 scanonly portions of the component 802, such as if quickly-evolving damageis occurring to those portions of the component 802. In some embodimentsthe controller 808 has the monitor 806 inspect the component 802 inpredetermined locations at predetermine intervals.

In some embodiments the readings gathered by the monitor 806 are storedin a memory 810 and can be sent to a remote source 814 such as viainput/output 812, which in some embodiments is operable to receiveinstructions from the remote source 814 and apply them to the controller808. In some embodiments the controller 808 analyzes readings from themonitor 806, such as by comparing them to predetermined values stored inthe memory 810. If the readings do not favorably compare to the storedvalues, then the controller 808 can send a report, such as signaling analarm, either through an interface 816 or to the remote source 814through the I/O 812. In some embodiments the remote source 814 makessuch comparisons.

Additional Descriptions

Various embodiments of the present invention integrate electricalconductors 104, such as refractory metal wires or other high-temperaturematerials, within the structure of a HTC. This ensures that theelectrical conductors 104 survive the fabrication of the HTC, retainsits signal generation and transmission capabilities, and does notnegatively affect the properties of the HTC.

In this manner, users will be able to more accurately evaluate thein-situ in-flight state of the components made out of the HTCs. Thiswill lead to a more accurate estimation of the lifetime of the componentwith respect to the remaining flight path, and an ability to optimizeits performance based on knowledge of the component's status. This canhave a direct influence on the survivability of the entire aircraft (as,for example, hypersonic platforms are often critically dependent oncertain hot-structure components), and ultimately impact the missionoutcome.

Potential commercial uses of the invention include various applicationswithin the aerospace industry, such as vehicle outer shells, leadingedges, high or low acreage thermal protection systems, enginecomponents, exhausts, hot flow-path components, missile cones, and soforth, and the power generation industry, such as land-based gasturbines, and nuclear power generation.

In various embodiments, the invention is incorporated into anyhigh-temperature ceramic or carbon-based HTC material component, and istherefore widely applicable. The design can vary according to thegeometry, complexity, composition, expected environment severity,operational rigor, and degree of required awareness for the component.

The teachings of the present disclosure provide means, methods andsystems for providing an awareness of the structural and compositionalstate of HTC-based components, before, during and after exposure toaggressive environments. It addresses the problem of uncertain componentlifetime in environments that are extremely difficult and expensive toreplicate in laboratory or industrial conditions. It provides real-timestructural performance information for the component, which can be usedto optimize the behavior of the supported overall structure. It alsoallows a means of evaluating the quality of as-processed HTC components,as well as their state after operational exposure.

Various applications include, but wouldn't be limited to, outer bodyshells of hypersonic vehicles (especially hot surfaces), internal hotsections of hypersonic vehicles (scramjet/ramjet engines, intake ducts,flow-path components, and so forth), conventional turbine enginecomponents, land-based power generators, smelting operations, andgenerally any application that requires structural and compositionalperformance in high temperatures and aggressive chemical environments.

One embodiment includes integration of electrical conductors 104 ofrefractory metal wires within the HTC, and more specifically between (orwithin) the plies 102 of ceramic fiber weave for a two-dimensionallay-up 100. There are various wire geometries and integration approachespossible, with two of the less complex ones shown in the figures. As theHTC component encounters a highly aggressive environment (such asatmospheric re-entry, atmospheric flight at hypersonic ornear-hypersonic speeds, turbine or scramjet/ramjet combustionenvironments, and so forth), the outer HTC plies 102 are worn away,which subsequently leads to the degradation and destruction of theelectrical conductors 104. The interruption of each layer of theelectrical conductors 104 is detected by the changes in the signals thatthey carry, and therefore provide a measure of detectable progress ofthe erosion front, and from there an estimate on the state of thecomponent.

Another embodiment includes modified native phases of one or morecomponents of the HTC, such as the matrix 106, fibers 108, or fibercoatings 110, instead of the introduction of an entirely new phase (themetal wires as described above). These modifications result in areas ofthe matrix 106, fiber 108, or fiber coating 110 that have propertiesthat are different than those of the surrounding environment (higherelectrical conductivity, for example). In this manner, components of theHTC itself serve as the sensors. As before, the sequential degradationof these selectively-modified HTC regions leads to interruption of thesignal going through them, thus providing an ability to track theprogress of the erosion front.

Yet another embodiment of the invention includes layers of electricalconductors 104 that are placed between each ply 102 of the HTC,resulting in a multi-layered sandwich-type structure, albeit with aminiscule proportion of metallic content.

The wire integration can be completed either before infiltration of thepreform (however the preform is shaped), or after individual layers havebeen infiltrated (and if desired, B-staged), but before cure andsolidification of the preform into a solid green body. The electricalconductors 104 can be placed manually or by automated means, and ifsmall enough, even co-weaved within a fiber fabric 102. Additionally,the electrical conductors 104 can be modified (by coatings, forexample), either to enhance the signal propagation, or to prevent themfrom reacting with the native HTCs phases, thus avoiding the formationof unwanted phases and degrading the sensory network performance.

The geometry of the electrical conductors 104 can be selected to bestfit the component shape, mission requirements and environment, requireddensity of coverage, cost-efficiency, and so forth. The electricalconductors 104 are located in one embodiment between each individual ply102 of the HTC and, context depending, the electrical conductors 104might also be highly localized or more irregularly distributed. In oneembodiment, the electrical conductors 104 extend outside the confines ofthe component to allow attachment to an appropriate readout device (forelectrical current, for example).

Generally, refractory types of metals are selected as the electricalconductors 104. Because of this and inert atmosphere processing,softening and oxidation during co-processing with the HTC are not aproblem. Rather, it is the possibility of reaction between the metal ofthe electrical conductors 104 and one or more of the native phasesforming unwanted compounds and degrading the performance of theelectrical conductors 104 and the HTC itself. As mentioned earlier, oneway to avoid this is to coat the electrical conductors 104 with acompound with which they are relatively stable. Another approach is toapply this method to HTCs that use native phases that are non-reactivewith the chosen metal.

The native phase modification can be achieved in several ways, dependingon the phase chosen for modification. If the matrix 106 is selected,this can be obtained by modifying the polymer (or using an entirelydifferent polymer) used to create the matrix 106, and selectivelyinfiltrating a small continuous volume of the two-dimensional fiberpreform, for example a thin strip along the length of the fabric 102.After this pseudo-infiltration, each individual, partially-infiltratedply 102 is cured, then the infiltration is repeated with thenon-modified polymer, this time filling the rest of the fabric 102 inthat same manner. This can be done individually to each ply 102, orcumulatively if the whole lay-up 100 is infiltration at once. Aftercure, the resulting green HTC will have a predetermined matrix volumecontent 112 with properties that are different from the rest of thematrix 106. In this case, separate leads can be connected to themodified areas 112 of the lay-up 100 in order to connect them to theappropriate read-out device.

If the fiber 108 is selected for modification, then this can be achievedby selectively applying a thin coating 110 over the already presentfiber 108 coating (if any), on a portion of the fibers 108 present inthe fiber weave 102. The coating 110 may be applied by any conventionaldeposition method, or as a slurry containing a phase with the desiredcharacteristics. Regardless of which coating method is chosen, it isperformed on the bare fabric 108, or on the fibers themselves beforethey are woven into a fabric, prior to infiltration so that the modifiedcoating 110 is fully deposited before the matrix 106 formation processis initiated.

After the new coat 110 is formed, the HTC processing continues along thetraditional route. Similar to the previous modifications, the goal ofthis is to introduce a continuous phase within the volume of the HTC,this time running along the surface of the fiber weave, with propertiesdifferent than those of the native constituents. Here, the fibers 108coated with the modified composition 110 extend beyond the edges of thecomponent so as to allow their connection to the respective read-outdevice.

Thus, the process is designed so that the newly-integrated or modifiednative phase retains through the HTC processing the properties that makeit unique with respect to the surrounding environment, and the abilityto transmit a signal. Additionally, no new, detrimental phases should beformed that affect the performance of the HTC (whether mechanical orenvironmental).

This problematic reactivity is potentially expected between theelectrical conductors 104 and the native HTC phases 102 and 106. Forexample, the possibility of at least one of carbide and silicideformation between the refractory metal electrical conductors 104 (Nb,Mo, W, Re, Ha, Ta, Pt, Zr, Hf, and so forth) and a carbon or siliconrich matrix 106 might require the implementation of a barrier coating insome embodiments, to prevent this from occurring. The concern is similarif the native-phase modification route is taken—if there is apossibility of reaction between the native constituents and thenewly-introduced polymer 112 or fiber coatings 110 (whether vapor orslurry deposited), measures specific to the materials selected are takenin some embodiments to prevent such reactions, in order to retain thedesired properties of the electrical conductors 104.

The electrical conductors 104 can also be formed by other depositionmethods, such as three-dimensional-printing a continuous conductivegrid, for example. A protective, or property-enhancing coating on theseparate phase can be formed by any conventional method—includingwithout limitation plasma, electron beam, vapor, slurry, andelectrophoretic. If a modified native phase, the modifications can beanything that changes the composition of the native phase, so that itacquires properties different than those of its native state. Modifyingthe matrix 106 forming polymer by adding solid particulates, mixing thatpolymer with one or more different polymers, using a completelydifferent polymer, or using a native polymer with modified composition,are all variations of the basic approach.

If using reactive melt infiltration, a certain volume 112 of the preformcan be of a composition that is different than the rest, so that uponinfiltration with the liquid material, the required new phase can beformed only at these locations. The second aspect of the native-phasemodification route (changing the fiber 108 or coating 110 of the matrix106), can also be obtained by any of the conventional depositionmethods.

The electrical conductors 104 geometry can be one-dimensional continuous(for direct readings), or discontinuous (for indirect readings such asinduction-based measurements), two-dimensional and three-dimensionalsensors, continuous or discontinuous, oriented through-thickness orparallel to the fiber weave direction, can also be integrated to provideadditional functionality, or fit the geometry of a specific component orneed. The native fiber composition can be carbon, refractory non-oxideor refractory oxide ceramic, and can be shaped in various orientations(1, 2, 2.5 or 3-dimensional geometries). The matrix 106 can be carbon,refractory non-oxide or oxide ceramic, and can be obtained by variousprocessing methods. Polymer infiltration and pyrolysis, (reactive) meltinfiltration, chemical vapor deposition, slurry-based infiltration, orany combination of these.

As long as it results in an integrated sensor network within the HTCcomponent, the ordering of the sensor integration and HTC processingsteps (sensor introduction, infiltration, cure, pyrolysis, and so forth)is not limited to a specific single sequence.

One use of the various embodiments according to the present invention isto detect structural and compositional degradation in HTCs that aresubjected to extreme environments. However, the electrical conductors104 can also be used for in-situ data collection from the component andits environment, ex-situ structural and compositional evaluation of HTCcomponents, evaluation of processing and fabrication methods for HTCs,impact detection—localized and widespread, and signal reception andtransmission.

Another embodiment of the invention involves variability in the formingof the metallic substructure. For certain applications (communicationsor directed energy protection, for example), more complex shapes andmorphologies of the electrical conductors 104 might be desirable, thatmight not be achievable by using long, straight, wire-like elements.There are a variety of additive-manufacturing-based methods that canrealize this, two examples being printing patterns with metallic-basedinks, or selectively laser-sintering metallic powders in certaingeometries onto the plies.

While fabric 102 consisting of woven ceramic fibers 108 is one optionalmeans of reinforcement, the fibrous pre-form 100 can be in a variety ofshapes and still accommodate the invention. For example, unidirectionaltape layup is a fiber architecture-based processing method that iscommonly used in the manufacturing of HTCs, and is very amenable to theincorporation of the electrical conductors 104 as proposed. Similarly,three-dimensional preforms that allow for the manufacture ofconsiderably thicker HTCs are also amenable to the incorporation of theproposed invention.

Embodiment of the invention can also be implemented to allow ex-situinspections of the HTCs, with the integration of the engineered metallicsubstructure, which permits non-contact (and non-destructive) inspectionsuch as by electrical or magnetic means (such as an eddy currentsensor), and to which pure ceramics or carbon composites are notsusceptible. In this manner, the integrity of the electrical conductors104 is inspected, and from there information about the state of thecomponent around that phase (the rest of the HTC) is inferred. In oneembodiment the electrical conductors 104 do not need to extend to theedges of the lay-up 100, but are distributed throughout the volume ofthe HTC. While the in-situ aspect may be useful from an operationalperspective, the ex-situ option may be useful for long-term maintenance,and life-cycle considerations.

The foregoing description of embodiments for this invention has beenpresented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdisclosed. Obvious modifications or variations are possible in light ofthe above teachings. The embodiments are chosen and described in aneffort to provide illustrations of the principles of the invention andits practical application, and to thereby enable one of ordinary skillin the art to utilize the invention in various embodiments and withvarious modifications as are suited to the particular use contemplated.All such modifications and variations are within the scope of theinvention as determined by the appended claims when interpreted inaccordance with the breadth to which they are fairly, legally, andequitably entitled.

REFERENCE NUMBER INDEX

-   -   100 Lay-up    -   102 Ply    -   104 Electrical conductor    -   106 Matrix    -   108 Fiber    -   110 Electrically conductive coating    -   112 Electrically conductive matrix

What is claimed is:
 1. A High Temperature Composite (HTC) having avolume comprising: a matrix material comprising at least one of ceramicand carbon, the matrix material comprising a first conductive portionand a second nonconductive portion, where the first portion and thesecond portion are non-intermixed, fiber comprising at least one ofceramic and carbon, the fiber dispersed within the matrix material; andwherein the first portion of the matrix material includes the secondportion of the matrix with an addition of a metal particulate to providean electrically conductive pathway within a portion of the matrixmaterial.
 2. The HTC of claim 1, wherein the first portion is disposedin a same position throughout a depth of the volume.
 3. The HTC of claim1, wherein the first portion is disposed in multiple positionsthroughout a depth of the volume, where the first portion disposed atone position in the depth does not contact the first portion disposed inanother position in the depth.
 4. The HTC of claim 1, wherein the HTCcomprises at least one of a surface, structural, propulsion, andfunctional component of an apparatus that is exposed to an aggressiveenvironment.
 5. The HTC of claim 1, wherein the fiber comprises plies ofwoven fibers.
 6. The HTC of claim 1, wherein the fiber comprises pliesof a nonwoven web of fibers.
 7. A High Temperature Composite (HTC)having a volume comprising: a matrix material comprising at least one ofceramic and carbon; fiber comprising at least one of ceramic and carbon,the fiber dispersed within the matrix material; wherein a plurality oflayers of matrix and fiber form the volume; and electrical conductorsextending across at least a portion of at least one of the plurality oflayers of the volume.
 8. The HTC of claim 7, wherein the electricalconductors comprise metal wires.
 9. The HTC of claim 7, wherein themetal wires form a grid pattern within the single layer.
 10. The HTC ofclaim 7, wherein the electrical conductors include metallic coatingsdeposited on to the fibers.
 11. The HTC of claim 7, wherein theelectrical conductors are formed into one or more of a plurality ofdifferent antenna shapes.
 12. The HTC of claim 11, wherein the differentantenna shapes transmits different radio frequency (RF) signals.
 13. TheHTC of claim 11, wherein an electromagnetic signal transmitted by theelectrical conductors distinguish a shape and a state of the electricalconductors.
 14. The HTC of claim 7, wherein the matrix material includesone or more carbon polymorphs including graphene and amorphous carbon.15. The HTC of claim 7, wherein the electrical conductors includeregions of the matrix containing conductive constituents includingparticulate, continuous metallic phase or modified ceramic phase that isdistinct from the remainder of the matrix.
 16. A High TemperatureComposite (HTC) having a lay-up volume comprising: a matrix materialcomprising at least one of ceramic and carbon; fiber comprising at leastone of ceramic and carbon, the fiber dispersed within the matrixmaterial; wherein a plurality of layers of matrix and fiber form thevolume; and electrical conductors positioned in an offset manner thatextends between one layer and into a next layer of the HTC.
 17. The HTCof claim 16, wherein the electrical conductors do not extend outside ofan internal portion of the lay-up volume.
 18. The HTC of claim 16,wherein the electrical conductors are detected with an inductive device.19. The HTC of claim 16, wherein the electrical conductors are formedinto one or more of a plurality of different antenna shapes.
 20. The HTCof claim 19, wherein the different antenna shapes transmits differentradio frequency (RF) signals.
 21. The HTC of claim 19, wherein anelectromagnetic signal transmitted by the electrical conductorsdistinguish a shape and a state of the electrical conductors.
 22. TheHTC of claim 16, wherein the matrix material includes one or more carbonpolymorphs including graphene and amorphous carbon.
 23. The HTC of claim16, wherein the electrical conductors include regions of the matrixcontaining conductive constituents including particulate, continuousmetallic phase or modified ceramic phase that is distinct from theremainder of the matrix.